Picture transmission



May 10, 1932- R. H. RANGER 1,857,330

PICTURE TRANSMISSION Filed Feb. '7. 19.29 2 Sheets-Sheet l ahvantoz RICHARD H. RANGER 351 his 61mm; 5 22 May 10, 1932. R. H. RANGER PICTURE TRANSMISSION Filed Feb. '7, 1929 2 Sheets-Sheet 2 51140214 601, RKHkRD H-RkNGER 32 m 61mm yg Patented May 10, 1932 UNITED STATES PATENT tori-E RICHARD ROWLAND RANGER, OF NEWARK, NEW JERSEY, ASSIGNOR TO RADIO COR- PORATION OF AMERICA, A CORPORATION OF DELAWARE PICTURE TRANSMISSION Application filed February 7, 1929. Serial No. 338,073.

The present invention forms a divisional part of my copending application, Serial No. 101,611, filed April 13, 1926, and relates to the transmission of pictures over a signaling 5 channel and particularly to refinements in I the method thereof.

' energy therefrom,

An object of my invention is to provide an improvement in picture transmission processes.

Y Another object of my invention is to provide means for increasing the detail of a transmitted picture.

Another object of my invention is to produce a picture composed of parallel lines of dots, dashes and spaces in which alternate lines produce an efi'ect of a darker tone than the intermediate lines.

In my copending-applications, Serial Nos. 695,175, filed February 26, 1924, and 7 26,235, filed July 16, 1924, I have disclosed'two modifications of a process for the transmission 0' pictures over a signal channel. In these processes, synchronized scanning and reproducing means are provided whereby the lights and shadows of a picture are analyzed by a photo cell and the total amount of light along a given narrow line,

is integrated to produce a series of current sponding pulses corresponding in spacing, or in both length and spacing, to the mean effective These curare then transmitted over a co venient signal channel and are caused to actuate a pen, moving in synchronism with the scanning means of the sender, whereby rows of marks are made upon paper correrent pulses to the light tones of. the origina picture. It has been found that excellent reproductionof pictures may be obtained by the process as disclosed in the mentioned applications.

My present invention, however, provides means for making a further improvement in the character of the resulting transmitted picture. In the process as described in the above mentioned applications it wasffound that the possible range of tone values in the reproduced prints was somewhat restricted by the necessity of providing marks in such positions as to outline the picture image, as

f the difference between the having variations well as the marks corresponding to the average tone values of the picture.

My present mventlon provides means for increasing the overall range of picture tone values in the transmitted picture.

Other objects and structural details of my invention will be apparent from the following description when read in connection with the accompanying drawings, wherein:

' Figure 1 is a diagrammatic representation of circuits and apparatus embodying my invention and Figure 2 is a modified form of circuits and apparatus embodying my invention.

Figure 3 is a diagrammatic representation of the circuits of my photo modulator of the previously mentioned applications with a; form of my present invention embodied therea diagrammatic indication of product as formerly made and a product of my present invention and,

Figure 5 is a picture reproduced according to my invention.

Figure 1 is Broadly the process of my invention consists in modifying the response of the photocell and amplifier above at the sending apparatus in such way that at successive intervals the pulses produced correspond to those which would normally be produced from aprint in a high light-key rate, and at another instant, variations in a low light-key with respect to the actual density atv the particular .point. This in effect is equivalent to varying thelength of spaces, or

1 the length of both the spaces and dots, corresponding to a given light intensity of the print.

In my first indicated embodiment the change in effective intensity occurs at the end of the line of scanning so that alternate cross lines of the recorded picture are alternately lighter than, and heavier than, the normal line provided by my ori inal system as previously disclosed. It is, owever, obvious that the heaviness of marking of two such lines gives a picture tone value which is very closely equivalent to the picture tone value of two lines of the former type of recorded picture.

in light intensity of the scanning light. It

may be produced by a small fluctuating light impinging directly upon the photo cell, or it may be produced by a change in the grid bias of any convenient amplifier triode incorporated in either the transmitting or receiving apparatus. Likewise the change in intensity, which may be called for convenience a bias, may be produced by a potentiometer control upon the grid of an amplifier.

triode, which shifts in value by the required amount at the end of each line of scanning under the control of the synchronous scanhing-drive mechanism or it may be shifted non-synchronously by any convenient device.

A'convenient means for providing this bias' is shown in Figure 1. A photo cell 1 is provided and connected to a battery 2 in series with an output resistance 3. Amplifying means as shown in the previously mentione applications amplifies the photo cell output through the agency of a triode amplifier 4.

my convenient grid biasing means for the triode 4 may be provided, such, for instance, as a resistance 5 inthe filament supply leads.

- A pair of potentiometers 6 and 7 are then connected to the biasing resistance 5 and provision made for setting the contacts thereon to give any desired negative bias to the grid of I the triode 4, by way of the photo cell circuit.

Leads are taken from the contacts of the potentiometers 6 and 7 to contacts of a relay .8,

the tongue of which is connected to the photo cell circuit and thereby to the grid of the triode 4. The coil of the relay 8 may be energized by any convenient portion of the circuits so that it will swing from one contact to the other at re ular intervals. This interval may be, as above described, that of the successive crosswise movements of the scanning means, in which case alternate cross lines will be predominantly alternately light and heavy as described. The otentiometers may then be adjusted by trial. One,No. '6, for instance, may be set to make the grid somewhat less negative than would normally be triode 4 under a set to make the done, whereby a heavier current flows in the photo cell 1. This produces a relatively greater number of pulses than normally, and therefore, a heavier line in the receiving device. The other potentiometer may then be grid somewhat more negative than normally, and in consequence under its above described given illumination of the control rather less current will flow throu h the triode 4 with a given illumination of t 0 photo cell 1, and therefore, a lighter line will.

be produ ced at the recorder. Alternation of control of the grid bias between the two potentiometers by the swing of the tongue of the relay 8 then gives the desired alternation nantly dark lines in the recorder.

This is conveniently shown by the representation of Figure 4, the upper portion a of urelfy in character since it has l een ound impossible to produce by hand a picture of the character produced mechanically bythe device of my invention.

- The actual result produced by the apparatus of my invention as herein disclosed is shown in Figure 5 which has been transferred to the drawings of this application by photomechanicalprocesses.

The embodiment shown in Figure 1 and produces a marked improvement in the character of the reproduced picture. It is, however, rather more regular in its variation between light and dark lines than is desirable.

The embodiment shown in Figure 2 provides a random change from light to predominantly dar lines and a change at a higher frequency than the embodiment of Figure 1, 'so that the change may occur in a random distribution in' the course of a marking of a given line.

'In this embodiment a photo cell 1 is providedasbefore with battery 2, output resistance'3 and triode amplifier 4. As before, a grid bias resistance 5 is provided. A potentiometer 9 is provided and connected across the ends of'the resistance 5'. In parallel with the potentiometer 9 is connected a second potentiometer 11 which is designed to have its contact arm continuously rotated by means of a motor 12 or other convenient device. An additional potentiometer 14 is provided and connected between the contacts of the potentiometers 9 and 11' with its own contact connected to the photo cell circuitand thereby, to the rid of the triode 4.;

In t 0 operation of this device the setting of the contact of the tentiometer 9 determines the average grid liias. The rotation of the contact of the potentiometer 11 then causes its contact arm'to take alternately the maximum and minimum negative bias which can be furnished by the biasing resistance 5;

' between predomlnantly light and predomiv redominantly '9 by an amount depending upon the value of the drop in the resistance 5, swing of the rotating potentiometer and the setting of the potentiometer 14; as will be obvious of inspection of the diagrammatic showing.

By either of these means the desired fluctuating marking line density is obtained at the reproducer and the desired improvement in detail and sharpness of outline of the reproduced print occurs. H

By Figure 3 of the arrangement herein disclosed I have shown the application of the arrangement disclosed by Figure 1 as applied to the showing of Figure 1 in the above mentioned copending application, Serial No. 726,235. It will be readily seen that the invention readily adapts itself to combination with a type of system disclosed by any of the circuit diagrams of the last named copending application.

While only the invention illustrated by Figure 1 has been combined with the showing in copending application, Serial No. 726,235, it will readily be seen that it is equally simple to combine therewith the showing of Figure 2 or other such modifications of the invention as may readily suggest themselves to those skilled in the art to which the invention relates.

Throughout the specification and claims, the generic term picture has been used to define the invention. It is, however, to be noted that the term ,picture is to be regard ed in its broad sense to include pictures, photographs, newspaper clippings or articles, magazine covers, finger prints, bank statements, financial statements, motion picture film records with or without the sound accompaniment, music scores, and, in fact, all types of written or printed matter which is capable of being viewed by the eye.

While I have shown but two embodiments of my inventions in the foregoing drawings and descriptions it is capable of various modifications therefrom without departing from the spirit thereof, and it is desired therefore that only such limitations shall be imposed thereon as are required by the prior art or indicated by the appended claims.

I claim as my invention:

1. A picture comprising a background of arbitrary light value having disposed thereon a field of markings arranged in substantially parallel lines, the spacing between lines thereof being fixed and the concentration of the various markings of the same line being varied to produce effects of varying light value, and the average massing of said field of markings being varied from line to line of the picture between predetermined limits to produce alternate lines lighter and darker itlhan the normal picture light value for each 2. A picture consisting of an area having disposed in rows thereon a mass of marks of light values different from the tonal value of said area, said marks being varied in concentration in proportion to different tone intensities on the picture surface, and the average massing of said marks being alternately more and less concentrated than that of the predetermined normal concentration of said marks for a normally suitable tone picture.

3. A picture comprising a mass of dots of uniform size varying in concentration in a manner to produce the effects of varying in tensities of light and shadow on one side of an arbitrary intermediate light value, and a mass of lines of unequal length equally spaced to produce effects of varying intensity of light and shadow for light values lying on the other side of said arbitrary intermediate light value, said dots and lines being arranged adjacent each other in a plurality of series of parallel marking lines and having the arbitrary light value used for determining the portion of the picture represented by dots and dashes changing from line to line be tween limits lighter and darker than the normal arbitrary light value.

RICHARD HOVVLAND RANGER. 

